The purpose of this study is to investigate the effects of Transcranial Direct Current Stimulation (tDCS) combined with watching a visual illusion on chronic pain due to spinal cord injury. The investigators hypothesize that active tDCS will reduce pain in subjects with spinal cord injury when compared to sham stimulation. The investigators will also measure changes in EEG data (alpha and beta frequencies) as well as motor cortex excitability.

Further study details as provided by Spaulding Rehabilitation Hospital:

Primary Outcome Measures:

Changes in EEG (alpha and beta activity) [ Time Frame: Measured for approximately 6 weeks ] [ Designated as safety issue: No ]

Determine whether treatment with tDCS coupled with visual illusion change cortical activity as assessed with electroencephalography (EEG). We hypothesize that tDCS plus visual illusion increase in alpha activity and inhibit beta activity and this will be associated with pain reduction in patients with moderate to severe below-level spinal cord injury (SCI) pain. EEG measurements will take place throughout the subject's participation in the study, measured at: baseline, immediately pre- and post- stimulation and at follow-up visits for a total of approximately 6 weeks.

Secondary Outcome Measures:

Changes in cortical excitability [ Time Frame: Measured for approximately 6 weeks ] [ Designated as safety issue: No ]

To investigate whether active tDCS combined with visual illusion induces changes in motor cortex and as indexed by single and paired-pulse transcranial magnetic stimulation (TMS) as compared with sham tDCS coupled with visual illusion. We will also determine whether these changes are correlated with the clinical outcome (pain reduction). TMS measurements will take place throughout the subject's participation in the study, measured at: baseline, immediately pre- and post- stimulation and at follow-up visits for a total of approximately 6 weeks.

Subjects will receive active tDCS while watching a visual illusion movie (legs walking on a treadmill). Stimulation will last for 20 minutes.

Procedure: Transcranial Direct Current Stimulation (tDCS)

Subjects will undergo tDCS stimulation. For both active and sham stimulation, we will use electrodes of 35cm^2, at an intensity of 2mA. For active tDCS, the subject will undergo stimulation for 20 minutes. For sham stimulation, the current will be ramped up and then down again (for 30 seconds total) to simulate the feeling of active stimulation.

Subjects will undergo tDCS stimulation. For both active and sham stimulation, we will use electrodes of 35cm^2, at an intensity of 2mA. For active tDCS, the subject will undergo stimulation for 20 minutes. For sham stimulation, the current will be ramped up and then down again (for 30 seconds total) to simulate the feeling of active stimulation.

Other Name: low intensity 1x1 direct current stimulator

Healthy Subjects

Healthy subjects will receive both interventions (active and sham) in a randomized and counterbalanced order. Each stimulation session will be at least 1 week apart to prevent carry-over effects

Procedure: Transcranial Direct Current Stimulation (tDCS)

Subjects will undergo tDCS stimulation. For both active and sham stimulation, we will use electrodes of 35cm^2, at an intensity of 2mA. For active tDCS, the subject will undergo stimulation for 20 minutes. For sham stimulation, the current will be ramped up and then down again (for 30 seconds total) to simulate the feeling of active stimulation.

Refractoriness to drugs for pain relief - such as tricyclic antidepressants, antiepileptic drugs and/or narcotics (pain resistant to at least 2 of these drugs supplied in adequate dosages for six months) (for spinal cord injury only)

Pain is not attributable to other causes, such as peripheral inflammation

Exclusion Criteria:

Clinically significant or unstable medical or psychiatric disorder

History of substance abuse

Neuropsychiatric comorbidities, including: Documented traumatic brain injury (TBI), defined as damage to brain tissue caused by an external mechanical force as evidenced by: loss of consciousness due to brain trauma, or post traumatic amnesia (PTA), or skull fracture, or objective neurological findings that can be reasonably attributed to TBI as assessed by the study PI

Implanted devices for pain control, such as vagal or deep brain stimulators

Contraindications to tDCS:

metal in the head

implanted brain medical devices

Pregnancy

Use of ventilators or ventilation support

Complete tetraplegic lesion (no motor function in the arms) (C3 to C8) as we will be measuring the motor evoked potential in the FDI (upper limbs); only tetraplegic patients with incomplete functional status and also as defined by the ability to elicit MEP in the FDI will be able to participate in this study

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Please refer to this study by its ClinicalTrials.gov identifier: NCT01404065